Differences in morphology between paralarvae in the Atlantic and Pacific suggest more than one species exists (Young et al. 1992), however, currently not enough specimens from different regions are available for proper species-level comparisons (Vecchione and Young 2008). Thelidioteuthis alessandrini is the misidentified juvenile form of this species (Bello 1992).

Justification:Ancistrocheirus lesueuri is an oceanic species which occurs in deep water and has a wide geographic distribution, although sub-species in the Atlantic and Pacific may exist. It is not, and is unlikely to be, the target of commercial fisheries and we therefore consider it to be Least Concern.

This species has a worldwide geographic distribution in tropical, subtropical and temperate waters (Roper and Jereb 2010), occurring in the Atlantic Ocean, Indian Ocean and Pacific Ocean. Its range extends into the Mediterranean Sea.

This is an oceanic species that shows sexual dimorphism in body size with females attaining up to 3.5 times the length and 10 times the weight of males (Arkhipkin 1997). Males typically live for up to 1 year whereas females can live for up to 2 years (Arkhipkin 1997). The number of ovarian oocytes range from 195,000 to 790,000 with a maximum oocyte diameter of between 2.0 and 2.2 mm (Laptikhovsky 1999). Planktonic juveniles are abundant in the upper mesopelagic and it is possible that spawning occurs near the sea floor near the continental slope or open ocean throughout the year (Arkhipkin 1997).

There are no conservation measures needed and none in place. Research is required to better understand the taxonomy and population demographics, as well as the life history and ecology of this species.